There exists a wide variety of sorting arrangements useful in article handling applications. In the field of integrated circuit handlers, the variety is limited generally to gravity-driven sorting arrangements. This is due primarily to the fact that current integrated circuit handlers are almost exclusively gravity-driven. That is, the motive force responsible for effectuating the movement of parts within the handler is gravity.
Sorting functions in a gravity-driven handler are commonly carried out by an apparatus analogous to a railroad track switch. An example is seen in FIG. 4 of U.S. Pat. No. 3,896,935, issued July 29, 1975 on an application filed Nov. 26, 1973. In this arrangement, the downward movement of an integrated circuit is directed into one of five paths of pivotally mounted "sorting finger". The fact that such arrangments are gravity driven and that they relay on changes in the direction of motion of the integrated circuits places severe limits on the throughput rates achievable therewith.
An alternate sorting arrangement for integrated circuit handlers is illustrated in U.S. Pat. Nos. 4,170,290 and 4,128,274, issued on Oct. 9, 1979 and Dec. 5, 1978, respectively, on applications filed on Feb. 28, 1977. Both of these patents are commonly assigned with the present invention. These patents illustrate a horizontally disposed "sort wheel" which has "pockets" thereon adapted to hold integrated circuits. Parts are dropped into the pockets under the influence of gravity. The wheel is then rotated until the part is over the appropriate output tube, at which time the rotation is stopped and the part drops from the pocket, again under the influence of gravity. While this sorting arrangement provides significant throughput improvements over the "railroad switch" arrangement discussed above, it still relies on gravity as the motive force. This reliance imposes throughput limits which, in turn, place lower limits on the costs of such operations as the final testing of integrated circuits.